Meet Tater

aka Tatie.
The first photo is when he was 2 and a half months.
The second photo is when he was roughly 4 months.
And the last 2 photos are the most recent he is now around 5 and a half, close to 6 months.
I was reading online about yorkie coats and I was just wondering if anyone could help me try and figure out what kind of coat Tatie has? It's a little bit coarser and wiry, but still touchable. His hair on his head is very soft while the hair on his back is a bit more coarse.
Also, what should I expect for the colors as he grows older? The color on his head is turning a light greyish white within the tan while there are sprouts of grey showing up on the rest of his black hair.

Thank you for your time!